The present invention relates generally to current references, and more specifically to process-independent current references.
Current references are circuits that are designed to provide constant current. The constant current is utilized in other circuits, and the design of these other circuits typically relies on the current being constant. One problem with current references is that the current provided can be sensitive to voltage, temperature, and process variations. That is to say, as the voltage, temperature, or process parameters (such as transistor threshold voltages) vary, the current generated by the current reference also varies.
Known current reference circuits exist that are relatively insensitive to voltage and temperature variations. See, for example, Sueng-Hoon Lee and Yong Jee, xe2x80x9cA Temperature and Supply-Voltage Insensitive CMOS Current Reference,xe2x80x9d IEICE Trans. Electron., Vol.E82-C, No.8 August 1999.
Some known current reference circuits also compensate for process variations. Existing process compensation mechanisms, which typically require the use of at least one package pin for an off-chip precision resistor, typically can achieve variations as low as +/xe2x88x925 to +/xe2x88x9210%. Typical variations in process uncompensated bias currents can be in the range of +/xe2x88x9230%.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a process-independent current reference that does not use an external precision resistor.